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audiocontr wrote:im familiar with the applicability (and crutchfield link) when it comes to 12v systems. How do the amperage/wattage ratings change when doubling the voltage?

It can be complicated depending on the device that is consuming the power. Passive devices, like resistors (heaters, simple RC filters (also depends on what is downstream of it)) will quadruple their power from 12 to 24 volts. P = V^2/R = Meltdown. Active devices, like a switching power supply, will have the same power at double voltage, but with half the current. So that really means you'll have to ask the manufacturer of the supressor/filter as to how it handles it.

Looks like the noise filters at Crutchfield seem to be rated for +12V only. But wait, isn't your stereo 12VDC? How about the intercom? That's where you want the noise filter: after the voltage converter (if it's 12V of course). Then if that doesn't work, try re-routing the wires for the stereo (maybe for the power converter, too). Parallel runs of wiring is very good a inducing noise from "noisy" wires. Anything with a coil is going to be noisy when it switches (solenoids, relays, and to a lesser extent fans and motors (depending on the mechanical load)). Anything with AC, too (though probably not a problem in a vehicle). More broadly, anything with a quickly changing current in the wire. Noisy both at the supply and as a radiated field (this is only prevelant in high-current and high-frequency stuff, usually. Spark plugs are a very fast impulse, which is easily radiated).

You may need a tune-up involving resistor-type spark plugs, shielded carbon-core spark plug wires, distributor cap, and coil.
Then if the DC supressor doesn't work, shielding the spark plug wiring. Then if that doesn't work, drink until you can no longer hear it. :idea:

(Parenthetical notation overload)

Good answer.

Appreciate the response. All items are 24 volts to include the stereo and intercom.

Its turning out to be a challenge locating 24v noise suppression devices. Maybe the stock one is the way to go.

Its turning out to be a challenge locating 24v noise suppression devices. Maybe the stock one is the way to go.

If the noise is conducted through the wiring, you can use the common 12V inductors that were intended to filter out alternator whine for the 24V power to your equipment; the inductor doesn't care what the voltage is, it only cares that the current is not exceeded. Put this in line with your 24V power source to each or all of your audio devices: http://www.radioshack.com/product/index ... e=Category
Then follow it with a 35V rated capacitor; the typical rule of thumb is to use 1,000 or 2,000 uf per amp of current draw. This scheme generally will usually kill noise on the power line.

I think the stock suppressor is intended to keep noise out of the truck's wiring harness. I don't think it will help with radiated noise; that is why the stock setup is a shielded ignition.

But if it is ignition noise that is radiated from the plugs and wires then you would be best served by 1) going back to the shielded stock system ($$$$!) or 2) getting good resistor wires and/or plugs as is done in modern vehicles. While I have resistor plugs/wires in my trucks, I still get a bit of ignition noise when I set my Ipod directly on the doghouse top. If I move it even 4-6" further from the engine then I can't hear the noise anymore.

Thank you Jim. I expect its a combination of both. I'll check the 12v noise suppressor suggestion.

What about a different angle... Is there anything i can line my dog house with to insulate the emitted noise?

Jimm391730 wrote:I think the stock suppressor is intended to keep noise out of the truck's wiring harness. I don't think it will help with radiated noise; that is why the stock setup is a shielded ignition.

Thanks Jim. Seems I was half right earlier, at least about the shielded ignition and radio noise. Whew! It's good not to feel too stupid...

24 Volt noise suppressor: $57.75

http://www.sportsimportsltd.com/nospfi.html

another for $25

http://www.ameradio.com/product/9477/description.html

Pinz, that second suggestion looks excellent! Thanks!

What about a different angle... Is there anything i can line my dog house with to insulate the emitted noise?

Radiated noise is electro-magnetic (radio waves, of a sort). The electro (voltage) portion can be shielded with any good conductive material but it must be well grounded to the truck chassis (no wimpy wires here). The magnetic portion is shielded with any magnetic material; sheet steel works, but the better the magnetic properties the better the shielding. "Mu-metal" is a brand name for 80% nickel magnetic shield material, but with such high nickel content it is very expensive and any mechanical stresses (bending!) ruins the magnetic properties.

Put simply, it is not easy to do this type of shielding!